Schaefer Manual Fan Speed Controller MSC-400 | 12.5A, 115/230V

Schaefer Manual Fan Speed Controller for Barns, Greenhouses and Grow Rooms

Schaefer built the MSC-400 as a single-output speed control for variable speed fan motors in agricultural, commercial and industrial buildings. It runs on either 115V or 230V AC, single phase, at 50/60 Hz. The rated load is 12.5 full load amps, enough to carry a whole row of circulation fans from one knob. The knob turns fan speed from low to high, and a separate ON/OFF toggle stops the fans without losing that setting. Inside the lid sit two trimmers, one for the high limit and one for the low limit. The low limit matters most, because it sets the slowest speed a motor can hold before it hums or stalls. Protection is built in, with a fused overload, transient protection and an RFI noise filter. The case is non-metallic, fire-retardant plastic sealed with a rubber gasket, so spray and greenhouse humidity stay out of the electronics. It measures 7 3/4 x 4 3/4 x 3 3/4 in and weighs about 4 lbs. Schaefer backs it with a two-year limited warranty from the date of manufacture.

Wiring and Tuning a Manual Variable Speed Control on a Fan Bank

Mount the box on a post or wall near the fans it feeds, where the knob is easy to reach on a walk-through. Schaefer calls for a qualified electrician to wire it, following the instructions packed with the control. Before anything goes on the circuit, add up the nameplate amps of every fan and keep the total inside that current rating. Eight circulation fans at 1.5 amps each, for example, land at 12 amps and leave a little headroom. On cool nights you can dial horizontal airflow fans down so they keep air moving across the canopy without chilling it. When the house heats up in the afternoon, the same knob brings them back to full speed in seconds. To set the floor, turn the knob all the way down, then adjust the LOW LIMIT trimmer until the slowest fan turns steadily. It will not suit every motor on the farm. Schaefer warns that small, highly inductive motors drawing 0.5 amps or less can jerk or lock, because the electronics are too strong for them. Check that each fan is rated for variable speed operation before adding it to the group. The same output can also dim up to five 250-watt incandescent heat lamps, which is useful over a propagation bench.

Key Features

• Dual-voltage 115V or 230V input: One model covers a 115V hobby house or a 230V commercial range on a single-phase circuit.
• 12.5 full load amps: A group of variable speed circulation or exhaust fans runs from one knob when their nameplate amps fit inside the rating.
• ON/OFF toggle switch: The fans shut down and restart at the same speed you left them on, with no need to find the setting again.
• High and low limit trimmers: You set the fastest and slowest points so every fan in the group runs smoothly at low speed.
• Fused overload and RFI filter: Fuse and transient protection guard the circuit, and the RFI noise filter cuts electrical interference from the speed control.
• Gasketed non-corrosive enclosure: The fire-retardant, non-metallic case with a rubber gasket holds up to humidity and wash-down in greenhouses and barns.
• Two-year limited warranty: Schaefer covers the control for its original owner for two years from its manufacturing date.

Technical Specifications